Pressure peak suppressors

ABSTRACT

This invention relates to pressure peak suppressors of the accumulator type for fluid pressure systems. The embodiment illustrated employs an elastomeric diaphragm in the form of a tube closed at one end by an integrally formed wall. The other end of the tube is covered by an end member to form a container for system fluid. Communication to the interior of the tube, or container, is afforded through an orifice in the end member. The diaphragm part of the container is arranged so that the incremental pressure required to deform it increases with the degree of its deformation. The end member is arranged so that less resistance is offered to flow out of the container. The diaphragm has uniform wall thickness over the length of its tubular section but the diameter of its central opening diminishes along its length. In the end member, the orifice increases in cross-sectional area in the direction from the interior to the exterior of the tube. The whole container is disposed within an outer housing or container.

United States Patent primary Examiner- -Laverne D. Geiger m AssistantExaminer-Richard J. Sher Attorney-Nien0w 81. Frater ABSTRACT: Thisinvention relates to pressure peak suppressors of the accumulator typefor fluid pressure systems. The embodiment illustrated employs anelastomeric diaphragm in the form of a tube closed at one end by anintegrally formed wall. The other end of the tube is covered by an endmember to form a container for system fluid. Communication to theinterior of the tube, or container, is afforded through an orifice inthe end member. The diaphragm part of the container is arranged so thatthe incremental pressure required to deform it increases with the degreeof its deformation. The end member is arranged so that less resistanceis offered to flow out of the container. The diaphragm has uniform wallthickness over the length of its tubular section but the diameter of itscentral opening diminishes along its length. In the end member, theorifice increases in cross-sectional area in the direction from theinterior to the exterior of the tube. The whole container is disposedwithin an outer housing or container.

PRESSURE PEAK SUPPRESSORS This invention relates to improvements inpressure peak suppressors for connection to pressurized fluid lines.

One object of the invention is to provide an improved accumulator forfluid systems, especially hydraulic systems. Another object is toprovide a novel structure for suppressing rapid pressure changes influid systems. In particular it is an object to provide a pressure peaksuppressor in the form of an accumulator which responds rapidly toabsorb system pressure increases and to dissipate energy input shocks ata relatively slow rate through the remainder of the fluid system. Inthis connection it is the object of the invention to provide anaccumulator the flow path to which offers a lower impedance to flow intothe container than is offered to flow from the accumulator. Further itis an object of the invention to provide an accumulator in the form ofan elastically deformable member the spring rate of which increases withthe degree of deformation. An accumulator with these characteristicsforms a pressure peak suppressor of a kind which is particularly usefulin the hydraulic braking systems of automobiles in that it serves toprevent application to the other wheels of the system any pressure peaksor spikes introduced into the fluid line by reactionary forces at one ofthe wheels. An object is to provide an improved pressure peak suppressorfor the use in automobile hydraulic braking systems and in thisconnection it is an object of the invention to provide a peak suppressorwhich can be mounted directly adjacent to the master cylinder of such asystem and which may be made in a size and a form that can beincorporated in the same housing with the hydraulic master cylinder ofsuch a system. Hydraulic positioning systems in which the output memberis a movable piston, are often employed in the situations wheresubstantial reactive forces are transmitted back into the fluid throughthe piston. Thus, for

example, the hydraulic systems employed in earth moving equipment, inshovels and scrapers and diggers and in hammers and the like oftenexperience very high input pressure peaks as a result of forcestransmitted to their fluid through the output member. Pressure peaksuppressors according to the invention are particularly useful to limitthe pressure peaks applied to the remainder of the system through thehydraulic fluid in those applications. Another object of the inventionis to provide an accumulator and pressure peak suppressor which isuseful in such systems and helps curb the deleterious affect ofhigh-pressure spikes and peaks.

The invention is not limited to use in pneumatic and hydraulic systemswhich accomplish position control. It is applicable to any pneumatic orhydraulic system in which high-pressure pulses are transmitted into thefluid of the system. The effect of such input pulses is to stress,possibly unduly, the elements and fittings of the system. In the case ofa system which includes several output elements each of which is to bepositioned, such for example as an automotive braking system, the resultcan be a position error manifested as a locked brake. Similarly,reaction to sharp input pressure pulses might be manifested as thebucking" of an arm or element in an earth moving machine or the like.

The input reactionary forcing function is likely to be quite complexranging from pressure spikes of short duration to slow ramp changes.Most often the input function can be expected to be broad bandedincluding components over a wide range of frequencies. The energy in thelow-frequency component can be expected to be substantially greater thanthe energy of the high-frequency components. In this connection it is anobject of the invention to provide an accumulator and peak suppressorwhich will serve as a very broad band filter to smooth out pressurechanges in fluid systems, principally in systems employing relativelyincompressible fluids. These advantages are achieved in the invention,at least in part, by the provision of a peak suppressor which includesan elastic member made to deform as an incident to system pressureincrease and the spring rate of which increases materially, although notabruptly, as the degree of deformation is increased. The flow path intoand out of the accumulator is arranged so that a greater impedance isoffered to flow in one direction than in the other direction.Application of these resistive and elastic forces introduces a time laginto system reaction to an input pressure change whereby an advantageouseffect is realized whether the restriction is arranged to providegreatest resistance to flow into or out of the accumulator. However thegreater advantage is proved when flow into the accumulator is relativelyunrestricted and flow from the accumulator is restricted. This featurecoupledwith a spring rate in the accumulator which does not obeyl-Iook's Law but in which spring rate increases with deformation,provides a very broad band filter or peak suppressor. These features ofthe invention may be combined with anotherLln preferred form theinvention invisions an accumulator one element of which exerts anelastic opposition to pressure changes when deformed and which isenclosed in a fluid filled chamber such that the fluid in the chamber,which is itself elastic, is compressed as an incident to. deformation ofthe elastic member.

In the embodiment selected for illustration the primary element of theaccumulator is a container whose'walls are made of an elastomericmaterial which is stretched when fluid flows into its interior as anincident to a pressure increase in the system external to theaccumulator. That elastomeric container is disposed within the cavity ofa sealed housing. The elastomeric container does not fill the cavity ofthe housing, the remaining volume being filled with air which may bepressurized in greater degree upon expansion of the elastomericcontainer. The effect of this construction is to place two accumulatorsin series. The second is formed to include the equivalent of africtional impedance in that energy used to compress the air in theseries accumulator is dissipated as heat. The quantity of energy thatcan be thus dissipated in a practical device is quite limited.Nonetheless, this feature of the invention becomes quite important inthe case of high-amplitude input forces of short duration which aresuperimposed upon lower frequency components of longer duration. Thissituation corresponds to the system being: jarred while under heavy loadand it is useful in that circumstances to dissipate the energy in thehigh-frequency component rather than merely to delay the time when thesystem must react to it.

All of these objects and advantages are realized in the invention by theprovision of a suppressor which is only connected to, and need not be inseries with, the fluid system which it protects. Other objects andadvantages of the invention will hereinafter appear upon examination ofthe following specifications in the accompanying drawing'in which:

FIG. 1 is an isometric view of a pressure peak suppressor embodying theinvention;

FIG. 2 is a top plan view of the unit of FIG. 1;

FIG. 3 is a cross-sectional view of the pressure peak suppressor takenon line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view taken through the flow distributorgland of the unit on line 4-4 of FIG. 3;

FIG. 5 is a cross-sectional view taken through unit on line 55 ofFIG. 3;and

FIG. 6 is an exploded view showing in cross section the elements of theaccumulator container and spacer.

The unit of FIG. 1 is arranged for use as an element'of an hydraulicsystem. The housing 10 is provided with a pair of flow openings by whichthe housing is connected in series with a hydraulic line. One of thoseopenings is visible in FIG. 1 where it is identified by the referencenumber 12. The accumulator or peak suppressor structure connects to thehydraulic line rather then being connected in series with it and iscontained within the left end of the housing in FIG. I. At the other endof housing 10, the right hand end FIG. I, the unit is provided with afluid line and valve structure 1.4 which also simply connects with thehydraulic line rather thenbeingin series with it. This is illustrated inFIG. 3 where the unit is seen to have an opening 16 arrangeddiametrically across from the opening 12. The housing 10 is generallycylindrical except that it has hexagonal shape externally of the housingin the middistance along its length. The hexagonally shaped portion isdesignated by the reference numeral 18 in the drawings.

In FIG. 3 the accumulator or peak suppressor part of the unit is shownat the right of the flow path openings 12 and 16 and the bleed valve andline 14 is shown at the left. The several elements inside the housingare assembled from its left end in FIG. 3. The right end of the housingis closed by an end wall 20 which is formed with a shallow recess 22centrally in the interior face of the wall 20. The first element to beassembled in the housing is the spacer sleeve 24. Next to be assembledinto the housing is the accumulator diaphragm 26. This diaphragm and thedisc 28, which overlies the left end of the diaphragm 26, form acontainer" for hydraulic fluid. The disc 28 serves as one end wall ofthe container and it is in this end wall that the flow opening affordingcommunication to the interior of the container is formed. That opening30 has a form of a orifice defined by the walls of the disc 28surrounding the orifice opening.

Abutting the left face of the disc 28 is the right end of a gland 32.The gland is provided at its left end with a shoulder 34 which seatsagainst the left rim or end of the housing 10. The gland extends pastthe openings 12 and 16 to the disc 28. That portion of the gland 32which lies in the plane of the openings 12 and 16 has reduced outsidediameter to form an annular flow path for fluid around the gland andbetween the two flow path openings 12 and 16. The peripheral wall aroundthe gland in this region has been designated by the reference numeral 36to facilitate its identification. The gland is provided with an axialbore or recess which is defined by the internal wall 38 and which opensto the right end of the gland. The diameter of that recess isapproximately equal to the diameter of the orifice 30 at the left faceof disc 28. Orifice 30 has a small uniform diameter at its side towardsthe interior of the diaphragm 26. But it widens at its side toward thespring gland so that its cross-sectional area becomes increasinglygreater toward the left face of the disc. Conversely, the diameter ofthe orifice opening decreases in the direction toward the diaphragm 26.

Communication between the inner recess defined by wall 38 and theannular flow manifold around the gland defined by wall 36 is affordedthrough four holes bored through the gland at right angles to oneanother so that the axes of all of them lie in the same plane. Thisplane is nearly coincident with the plane containing the axes ofopenings 12 and 16. These openings are best seen in FIG. 4 where theyare defined by walls 40, 42, 44, and 46 of the gland. The particulararrangement of this right end of the gland is not critical, it beingimportant only that the structure by symmetrical and arranged to avoidunequal pressure drops between the orifice 30 and the two hydraulic flowpath openings 12 and 16.

The gland 32 is provided with an axial, internally threaded bore 47extending from its left end toward the recess formed by wall 38. Thisrecess is connected to the recess formed by wall 38 by a smallerdiameter connecting opening 48. Opening 48 having a smaller diameter, ashoulder 50 is formed at the right end of the threaded recess. Thatshoulder serves as a valve seat for a valve head formed by the conicallyshaped end 52 of the externally threaded shaft 54. The shaft is providedwith a central bore 56 which opens at the left end of the shaft and isclosed at the right end. A lateral connecting passage 58 affordscommunication from the recess 47 through the opening 56. The shaft 54 isrotated to open and close the bleed valve formed by seat 50 and head 52to bleed air from the hydraulic system through the passageways 58 and56. Rotation is facilitated by a hexagonally shaped section 60 of thevalve shaft 54. Except when the hydraulic system is being serviced, thebleed valve remains closed.

Returning to the elements that form the accumulator and pressure peaksuppressor, the sleeve 24 serves as a spacer and as a support to confinethe diaphragm 26 against movement axially of the unit while permittingexpansion of its sidewalls. To this end of the sleeve 24 away from endwall 20 is provided with an inwardly projecting shoulder portion 62against which the outwardly extending flange portion 64 of the diaphragmis seated. The left face of the diaphragm 26 is recessed and boss 66formed axially at the right face of the disc 28 is disposed in thatrecess. In the preferred embodiment shown, the sleeve 24 and flange 64of diaphragm 26 have outer diameter so that they can be assembled with asliding fit into the housing 10. The disc 28 has an outside diametersufficiently great so that it must be forced or press-fitted intoposition against the flange 64 of the diaphragm. The gland 32 isencompassed by a sealing O-ring 68 to insure that the unit is sealedeven if the gland or the inner wall of the housing are not perfectlycylindrical. The gland has outside diameter sufficiently great so thatit too must be forced into position or press-fitted into position. inthis embodiment, assembly is accomplished while gland is cooled and thehousing is heated. To insure that the diaphragm is stable within thehousing it is provided at the right end, in FIG. 3, with a projectionhaving diameter to fit snugly within the recess 22. The projection isidentified by the reference numeral 70. in this embodiment the diaphragm26 is generally tubular in shape having an elongate central opening 71which is symmetrical about the central axis of the diaphragm and of theentire unit and which tapers toward the closed right end of thediaphragm at the projection 70. Thus, the cross-sectional area of thecentral opening 71 in the diaphragm 26 is reduced at successive pointsalong the opening away from the disc 28 and its orifice 30. Thethickness of the sidewall of the diaphragm 26 is uniform over the lengthof the diaphragm from its flange end to its closed end at the projection 70. Thus the tubular element which forms the diaphragm 26 hasthe shape of a Thus cone.

The spacer 24 can be considered to comprise an element of the housing.The end of the spacer rests against the closed end wall 20 of thehousing and at its other end the central opening of the sleeve is closedby the flange 64 of the diaphragm. Thus a cavity is formed within thehousing and the diaphragm 26 is disposed within that cavity. The innerwall of the spacer sleeve 24 is spaced from the outer wall of thediaphragm 26. Thus an air space 73 is provided into which the wall ofthe diaphragm can expand. The air in that space is trapped and will becompressed when the diaphragm is expanded.

While the embodiment selected for illustration in the drawingincorporates specific novel features which contribute to the objects andadvantages of the invention, this is but one of a variety of structuralarrangements that may be employed. The invention contemplatesincorporation of a container for fluid in its structure. That containermust have variable internal volume. Such a container may have only onewall or only a portion of one wall that is movable. Thus it may comprisea cylinder and piston arrangement or a syphon bellows or a simpledisc-shaped diaphragm or be otherwise arranged. In this embodiment thecontainer comprises a combination of the tubular diaphragm structure 26together with the disc 28. Certain portions of the diaphragm 26 serveonly to anchor the element in fixed position. It is primarily thesidewall section of the diaphragm that surrounds the central taperedpassageway and serves the function of a diaphragm in that it is movableto vary the internal volume of the container.

The invention contemplates that a change in the internal volume of the'container, at least a change to increase its volume, by opposed by someelastic force. That force may be derived from an element external to thediaphragm such for example as a spring member. Alternatively, that forcemay comprise the remittance of the material of which the diaphragm isformed. In this embodiment the diaphragm is made of an elastomericmaterial, such for example, as natural rubber or some syntheticmaterial. The embodiment selected for illustration is suitable for usein the hydraulic braking system of automobiles. lts diaphragm 26 is madeof rubber of 70 Durometer hardness.

Means are provided for permitting flow into and out of the container andthat means is arranged so that greater impedance to flow is presented inone flow direction than in the other. Advantageously less opposition isoffered to flow into the container. A variety of structural forms areavailable to accomplish this function. When the differential in flowimpedance is required to be great, partof the flow may be controlled bya one way valve system. In those instances when a relatively short timelag is sufficient, as in the case of an automotive system where theprimary purpose is to smooth out large pressure spikes, the requireddifferential in flow impedance is provided by arranging a structure sothat flow is less turbulent in one direction than in the other. In theembodiment selected for illustration, the disc 28 is provided with anorifice 30 which is shaped so that the flow experiences less turbulencein the direction into the container than is experienced when it flowsoutwardly from the container. This is accomplished by tapering theorifice opening so that its diameter is increased at successive pointsalong its length, or at successive cross-sectional places along itslength, toward the side of the opening away from the interior of thecontainer. At the interior of the container the opening 30 appears in aflat wall. That wall is arranged so that fluid within the container ispropelled toward the entire wall when the diaphragm 26 contracts toreduce its internal volume. The result is that flow in the region ofthat wall, the right face of the disc 28, is turbulent and the fluidexperiences more resistence in flowing out of the container than isexperienced in flowing into it. In this embodiment the opening is simplyconically shaped at the left. The surface can be curved at this point orotherwise shaped to reduce the impedance to flow into the direction intothe container if desired.

In a preferred form of the invention the elastic opposition to increasein internal volume of the container increases with successiveincremental increases in internal volume. This can be accomplished in avariety of ways, it being necessary only to insure that the spring rateof the elastic means increases with the degree of deformation of thatmember that supplies the elastic opposition. This is often done, forexample, by using nested springs successive ones of which experiencedeformation only after others have been deformed in some given amount.in the preferred form of the invention the elastic opposition isprovided by the renitence of the diaphragm material itself and it isaccomplished by structuring the diaphragm so that the elastic oppositionit exerts per unit of area force application differs in different areasof the diaphragm. This can be accomplished by varying the renitence ofthe diaphragm by using material of variable elasticity or by varying thethickness and by other structural arrangements. In the preferredembodiment illustrated, this is accomplished by using a diaphragm ofuniform wall thickness, the wall defining a tubular structure in whichthe inner opening has smaller cross-sectional diameter at successivepoints along its length, or at successful cross-sectional planes alongits length, so that the ratio of wall area to surface force applicationincreases along the length of the container. This construction resultsin a diaphragm which resists expansion more at its right end where itsinternal opening is smaller then it does at the left end where thediameter of the inner opening is larger. When fluid is forced into thecontainer under pressure the diaphragm tends to balloon at its endtoward the flange 64 before there is corresponding stretching andexpansion of the sidewalls of the diaphragm at its right end.

Advantageously the elastic means for opposing changes in the internalvolume of the container includes a resistence to such change in whichenergy will be dissipated as heat as an incident to a change to increasethe volume of that container. Many structural arrangements may beemployed to accomplish this function. The arrangement selected forincorporation in the embodiments shown in the drawings contributes tothe nonliniarity of the spring rate of that elastic means. The diaphragmis enclosed in a cavity which it does not fill. The remaining space isoccupied by a compressible fluid such, for example, as compressed air.Expansion of the diaphragm further compresses that air and heats it. Inthis embodiment the space between the inner surface of the spacer 24 andthe outer surface of the diaphragm 26 is filled with air which iscompressed somewhat durmg assembly of the disc 28 i be restricted exceptinsofar as is necessitated by the prior art and by the spirit of theappended claim.

lclaim:

l. A pressure peak suppressor for connection to a pressurized fluidline, comprising:

a container for fluid having variable internal volume;

elastic means for elastically opposing changes in internal volume of thecontainer; and

a fluid flow path communicating with the interior of said container andoffering greater impedance to the flow of fluid emerging from saidcontainer than to the flow of fluid into said container;

said container being formed with a relatively inelastic end wall wherebythe cross section area of said flow path remains unchanged in operation;

said container comprising an elongate, closed tube having sidewalls ofelastomeric material;

the ratio of cross-sectional area of the sidewalls to the crosssectionalarea of the interior tube opening defined by those sidewalls increasesat successive planes along the length of said tube away from said endwall.

2. The invention defined in claim 1 in which the inner opening defined bsaid tube has reduced cross-sectional area in the direction away fromsaid end wall, the thickness of said sidewalls remaining substantiallyuniform.

3. The invention defined in claim 2 which further comprises a housingformed of the cavity closed by an end wall; and which further comprisesa sleeve fitted within the said cavity against said end wall of thehousing, said sleeve having an annular inner surface and an inwardlyextending flange at its end away from said end of the housing; saidcontainer comprising a conical tube formed with an outwardly extendingflange at said end wall above the tube overlying said flange of thesleeve; said end wall of the tube comprising a disc overlying saidflange of the tube and having a central openings tapering along itslength to a larger diameter at its side away from said flanges.

4. The invention defined in claim 3 in which said end wall of thehousing is provided with a recess in which an end of said tube isdisposed, said housing being formed with passageways defining a fluidflow path communicating with said central opening of the disc.

5. A pressure peak suppressor for connection to a pressurized fluid linecomprising:

a container for fluid having variable internal volume;

elastic means for elastically opposing changes in internal volume of thecontainer; and

a fluid flow path communicating with the interior of said container andoffering greater impedance to the flow of fluid emerging from saidcontainer than to the flow of fluid into said container;

said elastic means comprising a defonnable member having a spring ratewhich increases with the degree of deformation;

said deformable member comprising the sidewall of said container, saidsidewall being fonned symmetrically about a center axis such that theratio of the cross-sectional area of the interior opening defined bysaid sidewalls increases at successive planes along the length of saidsidewalls.

6. The invention defined in claim 5 in which said sidewall of thecontainer are formed of elastomeric material of uniform wall thicknessdefining an interior opening deminishing in diameter at successivepoints along said central axis.

1. A pressure peak suppressor for connection to a pressurized fluidline, comprising: a container for fluid having variable internal volume;elastic means for elastically opposing changes in internal volume of thecontainer; and a fluid flow path communicating with the interIor of saidcontainer and offering greater impedance to the flow of fluid emergingfrom said container than to the flow of fluid into said container; saidcontainer being formed with a relatively inelastic end wall whereby thecross section area of said flow path remains unchanged in operation;said container comprising an elongate, closed tube having sidewalls ofelastomeric material; the ratio of cross-sectional area of the sidewallsto the crosssectional area of the interior tube opening defined by thosesidewalls increases at successive planes along the length of said tubeaway from said end wall.
 2. The invention defined in claim 1 in whichthe inner opening defined b said tube has reduced cross-sectional areain the direction away from said end wall, the thickness of saidsidewalls remaining substantially uniform.
 3. The invention defined inclaim 2 which further comprises a housing formed of the cavity closed byan end wall; and which further comprises a sleeve fitted within the saidcavity against said end wall of the housing, said sleeve having anannular inner surface and an inwardly extending flange at its end awayfrom said end of the housing; said container comprising a conical tubeformed with an outwardly extending flange at said end wall above thetube overlying said flange of the sleeve; said end wall of the tubecomprising a disc overlying said flange of the tube and having a centralopenings tapering along its length to a larger diameter at its side awayfrom said flanges.
 4. The invention defined in claim 3 in which said endwall of the housing is provided with a recess in which an end of saidtube is disposed, said housing being formed with passageways defining afluid flow path communicating with said central opening of the disc. 5.A pressure peak suppressor for connection to a pressurized fluid linecomprising: a container for fluid having variable internal volume;elastic means for elastically opposing changes in internal volume of thecontainer; and a fluid flow path communicating with the interior of saidcontainer and offering greater impedance to the flow of fluid emergingfrom said container than to the flow of fluid into said container; saidelastic means comprising a deformable member having a spring rate whichincreases with the degree of deformation; said deformable membercomprising the sidewall of said container, said sidewall being formedsymmetrically about a center axis such that the ratio of thecross-sectional area of the interior opening defined by said sidewallsincreases at successive planes along the length of said sidewalls. 6.The invention defined in claim 5 in which said sidewall of the containerare formed of elastomeric material of uniform wall thickness defining aninterior opening deminishing in diameter at successive points along saidcentral axis.